{{ range .AllTranslations }}
{{ if eq .Language $.Language }}
<a href="{{ .Permalink }}">{{ .Language.LanguageName }}</a>
{{ end }}
{{ end }}
Not sure what you want, but the above may be give you a hint. Also see https://github.com/letsencrypt/website/blob/master/layouts/partials/header.html#L33
Which builds language nav for the home page only.
There are written lots here and elsewhere about Go templates and scopes and the “dot”, so I will not go into detail.